#region Apache License
//
// Licensed to the Apache Software Foundation (ASF) under one or more 
// contributor license agreements. See the NOTICE file distributed with
// this work for additional information regarding copyright ownership. 
// The ASF licenses this file to you under the Apache License, Version 2.0
// (the "License"); you may not use this file except in compliance with 
// the License. You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
#endregion

using System;

namespace log4net.Core
{
    /// <summary>
    /// An evaluator that triggers on an Exception type
    /// </summary>
    /// <remarks>
    /// <para>
    /// This evaluator will trigger if the type of the Exception
    /// passed to <see cref="IsTriggeringEvent(LoggingEvent)"/>
    /// is equal to a Type in <see cref="ExceptionType"/>.    /// 
    /// </para>
    /// </remarks>
    /// <author>Drew Schaeffer</author>
    public class ExceptionEvaluator : ITriggeringEventEvaluator
    {
        /// <summary>
        /// The type that causes the trigger to fire.
        /// </summary>
        private Type m_type;

        /// <summary>
        /// Causes subclasses of <see cref="ExceptionType"/> to cause the trigger to fire.
        /// </summary>
        private bool m_triggerOnSubclass;

        /// <summary>
        /// Default ctor to allow dynamic creation through a configurator.
        /// </summary>
        public ExceptionEvaluator()
        {
            // empty
        }

        /// <summary>
        /// Constructs an evaluator and initializes to trigger on <paramref name="exType"/>
        /// </summary>
        /// <param name="exType">the type that triggers this evaluator.</param>
        /// <param name="triggerOnSubClass">If true, this evaluator will trigger on subclasses of <see cref="ExceptionType"/>.</param>
        public ExceptionEvaluator(Type exType, bool triggerOnSubClass)
        {
            if (exType == null)
            {
                throw new ArgumentNullException("exType");
            }

            m_type = exType;
            m_triggerOnSubclass = triggerOnSubClass;
        }

        /// <summary>
        /// The type that triggers this evaluator.
        /// </summary>
        public Type ExceptionType
        {
            get { return m_type; }
            set { m_type = value; }
        }

        /// <summary>
        /// If true, this evaluator will trigger on subclasses of <see cref="ExceptionType"/>.
        /// </summary>
        public bool TriggerOnSubclass
        {
            get { return m_triggerOnSubclass; }
            set { m_triggerOnSubclass = value; }
        }

        #region ITriggeringEventEvaluator Members

        /// <summary>
        /// Is this <paramref name="loggingEvent"/> the triggering event?
        /// </summary>
        /// <param name="loggingEvent">The event to check</param>
        /// <returns>This method returns <c>true</c>, if the logging event Exception 
        /// Type is <see cref="ExceptionType"/>. 
        /// Otherwise it returns <c>false</c></returns>
        /// <remarks>
        /// <para>
        /// This evaluator will trigger if the Exception Type of the event
        /// passed to <see cref="IsTriggeringEvent(LoggingEvent)"/>
        /// is <see cref="ExceptionType"/>.
        /// </para>
        /// </remarks>
        public bool IsTriggeringEvent(LoggingEvent loggingEvent)
        {
            if (loggingEvent == null)
            {
                throw new ArgumentNullException("loggingEvent");
            }

            if (m_triggerOnSubclass && loggingEvent.ExceptionObject != null)
            {
                // check if loggingEvent.ExceptionObject is of type ExceptionType or subclass of ExceptionType
                Type exceptionObjectType = loggingEvent.ExceptionObject.GetType();
                return exceptionObjectType == m_type || exceptionObjectType.IsSubclassOf(m_type);
            }
            else if (!m_triggerOnSubclass && loggingEvent.ExceptionObject != null)
            {   // check if loggingEvent.ExceptionObject is of type ExceptionType
                return loggingEvent.ExceptionObject.GetType() == m_type;
            }
            else
            {   // loggingEvent.ExceptionObject is null
                return false;
            }
        }

        #endregion
    }
}
